Neutralizing system for radio transmitters



" 0a. 27, 1931- L, 'E-B' RD 1,829,273

NEUTRALIZING SYSTEM-FOR RADIO TRANSMITTERS Filed Dec. 22, 1928 2 Sheets-Sheet 1 7M" E g I g I I INVENTOR. 530/1414 61 gefiia/w,

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TTORNEY Get. 27, 1931'. L. A. GEBHARD NEUTRALIZING SYSTEM FOR RADIO TRANSMITTERS Filed Dec 22, 1928 2 Sheets-Sheet 2 a J ww INVENTOR. 9865M) Patented Oct. 27, 1931 7 UNITED ST PATENT GFF'IiCE' LOUIS A. GE-BHARD, 0F WHSHTNGTO'N, DISTRICT'OFCOZUMBIA, ASSIGNOR"' DO WIRED RADIO, INC.) OF"1 TEW YORK, NI 1., A CORBO RATIONZOF DELAWARE NEUTRALIZING SYSTEM FOR BA DIO TRANSMITTER-S Applicationafiled Decembe1t:22,.1928.. Serial. No. 327,989..

, My invention relates to neutralizing systems in I general and more specifically to a method and system for neutralizing transmitting systems of the type employing thermionic tubes.

An object of my invention is to provide a systemby which radio transmitters employing thermionic tubes may be readily and easily neutralized.

Another objectof myinvention is to provide-a method. for neutralizing the thermionic tubes and associated circuits of a high frequency transmitter.

Still another object of my invention is to provide a system: for neutralizing thermionic tube circuits in-a high frequency transmitter whereby the correct potentials supplied the several circuits are automatically regulated by: the neutralizing system.

Other and further objects reside in the arrangement of the transmitter system and the neutralizing system employed therewith, a better. understanding of which can be had by referring to the specification following andto the accompanying drawings, wherein:

Figures 1 and 2 are diagrammatic illustrations showing the transmitting system and the neutralizing systemof my invention and Figs. 3 and 4 are schematic circuit diagrams showing thetransmittingsystem and the neutralizing system of myinvention.

In. high frequency. transmitters in. general the several parts are usually electrically shielded each from the other. In such transmitters employing thermionic tubes and associated input circuits, output circuits, and energy'supplycircuits, the shielding is necessaryto prevent interference between the several. circuits. It is'necessary to neutralize the several thermionic tube circuits and provide the. proper. balance of the inter-related circuits. In transmitters where 1 each individual thermionic tube is shielded inrespect to the other and where the transmitter in its entirety is so shielded, it is often diflicultto determine the balanced condition. The I removalofthe shielding from a section of the transmitter causes an unbalanced condition which-when corrected with. the shielding removedwillbeunbalanced when the shielding isreplaced. The neutralization maybe most conveniently accomplished by connecting to the input and output circuita condenser the capacity of which can be varied tocounter-balance the capacity of the interrelated electrodes and associated circuit constants. The balanced condition is usually observed by. noticing an i improvement. in .the overall efficiency of the transmitter, which is only anindirect indication of theneutralized condition. To employ individual means assocated with the. respective thermionic tubes and-their associated circuits af fordsa more accurate means for determining the condition of balance. This method, however, introduces certain difficulties in-. cluding the. first mentioned inconvenience of removing the shieldingandthe losscaused by. the indicating means and possible damage thereto fromhigh frequency energy. The neutralizing system of my inventionavoids the. foregoing difficulties and. affords an. efficient and. accurate means for determination of the balanced condition.

' Fig. 1 of the accompanying .drawings showsztwo units land la of arradio transr mitter in 1 partial cross-section. Inductances 2 and 2a are included inunitsl andlarespectively and comprises portions of the high frequency circuits associated with individual thermionic tubes. Inductances .6 and 6a. are associated with inductancesQandiQa respectively whereby high-frequency energy'will be transferred between inductance2 and inductance 6 andbetween inductance 2a and. inductance 6a. The terminals of inductance 6 are connected'to contact members 7 a. The terminals of inductance 6a areconnected to contact. members 'Zab. Contact members .7 a and'a'ab are adapted to receivesuitable contacting members. associated with. an indicating device and are electrically insulated each from the other and insulated from the metal shielding of. the respective units. .Fig. :2is-a diagrammatic illustration sh'owingthe. indieating device employed in theneutralizing system and method of my inve-ntion. The indicating device inits enti'rety may be en closedin a suitable container 10a which may be of metal or'of sutableinsulating composition. The-indicating device'co'mprises conter 9 and container 10a.

tacting members 7, capacity 8, indicating mehe several constituent units are interconnected as shown in Fig. 3 of the accompanying drawings.

Fig. 3 shows a representative circuit arrangement schematically representing one of the units 1 or 1a of Fig. 1. Thermioiiic tube I 1 having cathode 18, controlelectrode 19 and anode electrodes'20 is associated withsuit able energy supply circuits and high fre-.

quency circuits. ,The input circuit of; thermi'onic tubel comprises inductance 2a and 27" which maycomprise a suitable thermionic capacity 16'1111'i61CO1111C1'/1I1g cathode 18 and controlelectrode Inductance2a is associated-with source of high-frequency energy tube system. The frequency characteristics of inductance 2a niay besuitably adjusted by'mea'ns of capacity 18. Capacity 16 serves Y ca amity-e; "A load'circuit 5 is associated With induc'tanc'e'2 and may comprise theinput'cirsuit of; a thermionic tube amplifier, a wired radio circuit or a space radio'radiating'system'as shown. Capacity 11 isassociated with inductance -Q2aand anode 2O.- Adjustments of capacity 11 provide: different conditions of balance betwee nranode 20, cathode 18,'con

' trol electrode 19-and the respective associated circuits;v Inductance 6 is associated with inductance 2 whereby high frequency energy may be transferred thereto. Indicating device .10 comprising contacting members 7'," meter 9 and variable condenser 8 is ad ust ably positioned in respect to contact memhers 7 a. Inductance 6a is positioned in'in ductive relation to inductance 2a and is elec trically connected to contact members 'Tab. The operation of the transmitting system and method for neutralizing the system, schematicallyillustrated in Fig. 3, is as follows: 'Sources14, 15 and 27' are connected to thermionic'tube 1 and associated circuits.

Source ofv anode potential 17 is not connected to the tube at this time. Input circuit 2a, 13

- y is adjusted to resonant frequency. Balance condenser 11 is adjusted to some value be- ,lieved to be near'that required for. balanced.

7 I Output circuit 2, 3 is adjusted to a frequency which is approximately the resonant fre quency. Indicating device 10 isadjusted to a frequency value differing from the above mentioned resonant frequency. Indicating 7 7 device 10 now connected with inductance from contaet-r m'embersfitt butiare inechanmaximum deflection'when circuits 2a13 and 2- 3 have approximately the same frequency characteristics. Condenser 11 is now adjusted to a value whereby the ii1d1- .cated. reading of meter 9 is reduced. If this j reading is of too low a value condenser 8 may be adjusted so that the circuit 6, 8 and 9 Willhave frequency characteristics more nearly corresponding to the high frequency energy. The. frequency characteristics of circuits 2a, '13 and 2, 3' are 110W adjusted to the proper valuesa This process of'adjustments is repeated until the proper adjust merits are obtained, at which time an increase or a decrease in the'capacity" value of coin denser 11 causesa corresponding iiicrease g in the readingiof meter v Flg- 4 1S a Schematic circuit diagram showing the neutralizing system for radi t 'mitters of my invention. Therinionic tubes 1 1a, 1b and 1c are employed insuitable amplifier circuit arrangements associated with source of high frequency energy 27. Tlierinionic tubes 1, 1a, 1b and 10 are illustrated as of tlie'three-electrode type, however,it is obviousthat thermionic tubes einployi'ng four or more electrodes may be employed. Therinionic' tube 1 is energized from sources '14, 15 and 17 thermionic tube 111 is energized from sources 1%, 15a and 17; thermionic tube 1?) is energized from sources 14?), 15band 17, and thermionic tube 10 is energized from sources 140, 150 and 17.

Load circuit 5is associated'with inductance 2 and may comprise'the input circu t of a thermionic tube, a wired radio system or a space radio radiating system as shown. The

individual thermionic tubes and associated input and output circuits are'bala'nced by means of "condensers 11, 11a, 11b and 110. The frequency characteristics of" the input and output circuits are controlled by means of 'in-ductances 2,-2a, 2b-and 2c and capacities3, 3a,'3b and 30 respectively. The'supply of anode potential to thermionic'tubes 1,

1a, 1b and 10 is controlled by individual relays 21-22 21a'22a, 21Z2-226 and 210- 22c, respectively; Source 25 supplies the necessary energy for actuating electro' magnet's '21, 21a, 21b and 210 by means of contacts'24. Contacts 24 are'engaged by means of electromagnet-28 which is energized from source 25jby-mo'mentary contact switch 26. Fig. 4 showsthe indicating device comprisin g condenser 8, meter 9' and contacting members 7a and inductance '6a. Auxiliary contact; members 12 are opened bythe engagementor members 7 and 7a thereby interrupting the anodesupply-- circuit of thermionic tube; lai Contact'ineinbers' 12 arelinsulated ically connected thereto by suitable insulati gvmembers. Contacting members 7 and associated circuit 89 are adapted to be connected to contact members Tab. The latter position causes contact members 12a to open which deenergizes electro'magnets 21a and 21?). The deeiiergization ofelectromag net 21?) allows contact members 22?) to open thereby deenergizing the anode circuit of thermionic tube 15. Similarly contact nieinbers 7 may be caused to engage with contact members 'z'abc which would cause contact members 126. to open. Electromagnet 210 would be deenergized which would allow contact members 220 to open and cause the deenergization of the anode circuit associated with thermionic tube 10. Electromagnets 21a and 21?) are also deenergized.

The method of neutralizing or balancing the transmitting system of my invention'is schematically illustrated in Fig. i. The indicating device comprising contacting members 7, variable condenser 8 and meter 9 is engaged with contactmenibers 7a. The

- anode potential supply to thermionic tube 1a is simultaneously and automatically removed. Circuit 2b3b is adjusted to resonant frequency, Balance condenser 11a is adjusted to some value believed to be near 5 that required for balance. Circuit 2a-3a is adjusted to a frequency which is approximately that of the resonant frequency. Circuit 6a'' 78f9 is adjusted to a frequency value differing from the above mentioned resonant frequency and later adjusted to a frequency value more closelycorresponding to the resonant frequency. Meter 9 will have a maximum deflection when circuit 2a-3a and -2b-3b have approximately the same frequency characteristics. Balancing condenser 11a is now adjusted. to a value where by the indicated reading of meter 9 is reduced. If t iis reading is of too low a value, condenser 8 may be adjusted so that the circuit 6a789 will have frequency characteristics more nearly corresponding to the high frequency energy. The frequency characteristics of circuits ike-3a and 2h3?) are now adjusted to the proper values. This process is repeated with each of the circuits associated ith thermionic tubes 1?) and 1c and in each instance the adjustments are continued until an increase or decrease of capacities 11a, 11?) or 11c causes an increase in the reading of meter 9 when associated with the respective circuits. The anode potential is automatically removed from the succeeding thermionic tube amplifier circuits when adjustments at the particular time are being made.

The method and system for neutralizing or balancing radio transmitters of my iiivention offers many advantages. No part of the transmitter need be removed during the process of neutralizing. The state of balance may be readily determined by the" attending operator and may be corrected without undue delay and complicated procedure by his merely inserting the indicating device in the plug receptacles exposed in the various transmitter panels or connected to the various circuits. Suitable Contact members may be associated with such plug receptacles whereby an artificial circuit is connected to the respective energy pick-up coils when the indicating device isiiot inserted in that particular circuit at the time.

I realizethat many modifications of my invention are possible without departing from the spirit of my invention and it is to be understood that my invention shall not be limited to the accompanying drawings or the foregoing specification but only by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A method for neutralizing radio transmitters employing a multiplicity of coupled thermionic tube circuits comprising the steps of adjusting the frequency characteristics of the input circuit of a selectedtube, simultaneously deenergizing the anode supply circuit of the selected tube connecting a cir cuit to said input or output circuit for determining the relative energy therein adjusting the frequency characteristics of the input and output circuits to obtaina maximum indication of energy, adjusting the relative capacity between said-input and output circuits to obtain a relatively minimum value of energy in said output circuit 'restoring the anode supply circuit andrepeating the above mentioned stepswith each of said multiplicity of coupled thermionic tubes.

2. A method for neutralizing radio transmitters employing a multiplicity of coupled thermionic tube circuits comprising the steps of adjusting the frequency characteristics of the input circuit of a selected tube, simultaneously deenergizing the anode supply circuit of the selected tube while maintaining the cathode circuit in energized condition, determining the relative energy in the output circuit, adjusting the frequency characteristics of theinput and output circuits to obtain a maximum indication of energy, adjusting the relative electrode capacity of said thermionic tube to obtain a relatively minimum value of energy in said output circuit restoring the anode supply circuit and repeating the above mentioned steps with each of said thermionic tubes.

3. A neutralizing system for signaling a with contacting members, an indicating device comprising a meter andan ad ustable capacity and j means for connecting said indicating device withsaid contacting members. 1 Y

' 4. 1 1 method for neutralizing radio transmitters employing a multiplicity of thermiio'nic tube circuits comprising the steps of mentioned steps with each of said thermionic tubes. c l V 5. A method for neutralizing-radio transmitters employing a multiplicity of thermionic tube circuits comprising the steps of ad usting the frequency characteristics of the input circuit'of a selected thermionic tube circuit,simultaneously reducing the anodeto substantially zero potential for the selected thermionic tube, determining the relative energy in the output circuit, adjusting the frequency characteristics of the input: and out put circuits to obtain a maximum indica v tion' of energy, electricallybalancing the 7 relative electrode capacity of saidfthermi- 'onic tube to obtain. a relatively minimum valueof energy in said output circuit, restoriling the anode supply to said tube and. repeating the above mentioned steps with each of said multiplicity of thermionic tubeslin succession. e v p p 6. A neutraliz ng system for transmitters employing thermionic tubes compris ng in 'ccmbiiiation a plurality ofqhigh frequency output circuits EISSOCIZLtGClWVllZll said thermij onictubes, aplurality of inductancesgassociated with said output circuits, a plurality of contact members associated .with.-said ina ductances and an adqustable capacity electrically connected with an indicating device, said" capacity and indicating device being connectible withsaid first mentioned contact inembers.-

LA neutralizing system for thermionic tube high frequency transmitters comprising in combination. input'and output circuits, an auxiliary inductance circuit assoc ated therewith, plate circuit potential supply said plate circuit potential supply means in the particular outputcircuit with which said indicating device is selectively connected.

' 8. A neutralizing system for thermionic tube high frequency transmitters comprising incombination a plurality of auxiliary inductances associated with thehigh frequency circuits of-said thermionic tubes, circuits for an indicating circuit comprising a meterand an adjustable capacity adapted to be connected with either of said auxiliary inductances, while automatically disconnecting the plate potential supply to the particular'tube to which said'last mentioned auxiliary in-- ductances are'connected.

9; In a neutralizing system for radio transmitters employing thermionic tubes the comfsupplyingplate potential to said tubes, and I bination ofauxiliary inductances associated v with the high frequency circuits of said tubes, power supply means for the plate circuits of said tubes, said inductances being electricallyconnected' to individual groups of contact members and an indicating apparatus comprising energy indicating means and an ad ustable capacity adapted to be selectively connected with said individual groups of contact members, while automatically disconnecting said power supply means from the H plate circuit ofone of said tubes."

10. In a neutralizing system' for radio transmitters employing thermionic tubesthe combination of-auxiliary inductances associaied with the "high frequency; circuits of V saidltubes, energy supply circuits for said 'tliG-IZiliOlllC tubes, said inductances being elec tricaliy connected, to individual groups of contactmembers, and an indicatingapparatuscomprising energyindicating means and c an adjustable capacity adapted to' be r selec tively associated with said individi'ialgroups of 'contact members, said groups of "contact members be ng mechanically associated with other cont-act members adapted to control p the energy supply circuits to the above mentioned thermionic tubes when said indicating apparatus is associated with said first mentioned contact members.

Y LOUIS A. GEBHARD.

means for said output circuits, said auxiliary inductance circuit being provided witlilcon tacting membersadapted to receive other contacting "inembersaconnectedwith i an energy 7 indicating device and an 'adjustable capacity andmeans for interrupting the connection of 

